Quality of SS347 material
Thread Content
For SS347 material quality, why is the Nb content required to be 10 times that of carbon, but not more than 1.1%?
Nb exerts an anti-sensitization effect in the form of carbides, which serves to provide corrosion resistance; the carbon content in 347 is 0.03–0.08, while that in 347H is 0.04–0.10. If we consider 10 times the carbon content of 347H, it amounts to 1.0, with a maximum value of 1.1. The nominal Nb content of 347H is 8 times that of carbon, which reduces its corrosion resistance slightly but increases its high-temperature resistance.
I don’t understand; the chemical composition of SS347 stainless steel should be fixed, so why is this requirement needed? Is it related to some specific project?: o
The role of Nb in stainless steel is to remove excess carbon from the steel and prevent susceptibility to intergranular corrosion after sensitization treatment; therefore, it is directly related to the carbon content in the steel. Excessive Nb will precipitate in the form of dendrites near the grain boundaries, thereby increasing susceptibility to intergranular corrosion.